Poa annua and annual bluegrass weevil damage

Poa annua is the preferred host grass for the annual bluegrass weevil to lay eggs and for larval development while 007 creeping bentgrass is most tolerant.

Photo: Annual bluegrass weevil larvae.

Research conducted at Rutgers University, under the direction of Dr. Albrecht Koppenhofer, on the annual bluegrass weevil shows a preference for turf consisting of Poa annua over 007 bentgrass for egg-laying and larval development.

Golf course superintendents who manage golf course turf in the Mid-Atlantic and Northeast US and eastern Canada have experienced severe damage from weevils each year on Poa annua greens, collars, approaches, tees, and fairways.

Over the past decade golf course superintendents have relied on use of pyrethroid insecticides for control, however, overuse of this class of insecticides has led to highly resistant populations of the annual bluegrass weevil on many golf courses. At this time many golf courses cannot use pyrethroid insecticides as they currently do not provide effective control of the annual bluegrass weevil.

Additionally, pesticide resistance is not specific, with most of the available insecticides shown to be less effective against resistant populations of the annual bluegrass weevil.

Dr. Koppenhofer states, "relying only on chemical control for annual bluegrass weevil is not sustainable."

Rutgers research concludes that 100% creeping bentgrass to be more tolerant to weevil larval feeding than mixed stands of Poaannua and creeping bentgrass.

Reducing the percent of Poa annua in a turf in favor of more creeping bentgrass or a total conversion to bentgrass should be the best way to reduce turf damage from the annual bluegrass weevil.

The Rutgers findings report that it is important to select bentgrass varieties that are not only more tolerant to the annual bluegrass weevil feeding but also poor hosts for the annual bluegrass weevil.

007 creeping bentgrass was among the most tolerant to annual bluegrass weevil larval feeding of all the species tested at Rutgers. 007 was also reported to have the most aggressive growth habit and showed the faster recovery from environmental stress and pest damage of the bentgrasses studied.

Photo: Annual bluegrass weevil adult.

Relying only on insecticides for control of the annual bluegrass weevil is not a desirable strategy at this time.

As 007 bentgrass is among the most resistant and tolerant to the annual bluegrass weevil this variety is the best choice for Poa annua conversions to bentgrass. Additionally, Penncross bentgrass was reported to be significantly inferior to 007 and much less desirable for use.

Previous research conducted at Rutgers has found that interseeding timing for bentgrass into a Poa annua turf is recommended from mid-June to July, which coincides with the period of greatest damage by the annual bluegrass weevil larvae on Poa annua. Improved results will be achieved if annual bluegrass is weakened to ensure better creeping bentgrass establishment.